Pentagon investigates top U.S. commander in Afghanistan

• Allen is under investigation for alleged "inappropriate" emails with a woman involved in Petraeus' scandal.

• Panetta said Allen will remain commander of the ISAF while the case is under investigation.

• Petraeus resigned last Friday after admitting an extramarital affair.

File photo taken on March 20, 2012 shows John Allen, commander of the U. S. and NATO forces in Afghanistan, testifying before the House Armed Services Committee on Capitol Hill in Washington D.C., the United States. The top U.S. commander in Afghanistan has been put under investigation for alleged "inappropriate" communications with a woman involved in the scandal that forced out CIA Director David Petraeus. (Xinhua/Fang Zhe)

WASHINGTON, Nov. 13 (Xinhua) -- The top U.S. commander in Afghanistan has been put under investigation for alleged "inappropriate" communications with a woman involved in the scandal that forced out CIA Director David Petraeus.

U.S. Defense Secretary Leon Panetta said Tuesday that he has directed the inspector general of the department to open an investigation of General John Allen after the FBI referred a matter involving him to the Pentagon on Sunday.

Allen will remain commander of the International Security Assistance Force (ISAF) while the case is under investigation, said Panetta, adding that the case should also be notified to the U.S. Senate Armed Services Committee.

Allen became the ISAF commander and commander of U.S. forces in Afghanistan in July 2011. His nomination to be the next commander of U.S. European Command and the commander of NATO forces in Europe is put on hold until relevant facts are determined.

Panetta has also asked the ranking members of the Senate Armed Services Committee to delay the scheduled confirmation hearing on Allen's pending nomination.

"Obviously, it was a very sad situation, to have a distinguished career like that end in this manner," said Panetta on Monday en route to Perth, Australia, referring to the resignation of Petraeus.

ABC news quoted a senior defense official as saying that the FBI has uncovered thousands of alleged "potential inappropriate" emails between Allen and Jill Kelly, a central figure in Petraeus' scandal.

Petraeus's announcement of resignation last Friday after confessing to an extramarital relationship shocked Washington.

Media reports over the weekend said that the FBI began investigating the case after Kelly, a friend of the Petraeus family, complained to law enforcement about receiving anonymous and threatening emails. The FBI traced the emails to Paula Broadwell, Petraeus's biographer, and then discovered that Broadwell was Petraeus' girlfriend.

Petraeus, a retired four-star general who served more than 37 years in the U.S. Army, took the office as the director of CIA in September, 2011. He had overseen all coalition forces in Iraq and led the military campaign in Afghanistan.

U.S. lawmakers on both sides have criticized the FBI for not notifying the Congressional intelligence and security panels of the probe into Petraeus's scandal.

Democratic Senator Dianne Feinstein, chairwoman of the Senate Intelligence Committee, said on Monday that her concern about the case had escalated over the last few days as more details popped up.

The panel, she said, will investigate why the FBI failed to alert the panel immediately about Petraeus's scandal.

WASHINGTON, Nov. 13 (Xinhua) -- The White House on Tuesday said that President Barack Obama still backs John Allen, the U.S. commander in Afghanistan, to take over as Supreme Allied Commander Europe -- the top military position in NATO.Full Story

WASHINGTON, Nov. 9 (Xinhua) -- U.S. President Barack Obama on Friday accepted the resignation of David Petraeus, director of the Central Intelligence Agency (CIA), according to a White House statement.Full Story